1. Field of the Invention
The present invention relates to medical, operating room power drills which are typically used in conjunction with X-ray machines for drilling precisely-located holes in bone for receiving and anchoring prosthetic implants. More particularly, the invention relates to a radiolucent, e.g. X-ray transparent, drill assembly and targeting drill bit for allowing the holes to be drilled more precisely.
2. Description of the Related Art
Certain surgical procedures require that a surgeon drill and/or place wires, pins or screws (or some other component) through bones or implants which cannot be completely seen without the use of X-ray equipment. For example, when an intramedullary nail is inserted in the medullary canal of a bone, it may be necessary to lock the end of the nail in place by inserting retaining pins, also called transfixion screws or transverse locking screws, through interlocking holes at the distal end of the nail. It is important in the interlocking of intramedullary nails that the orthopedic surgeon know the precise position of the interlocking holes in the nail when drilling through a bone to avoid unnecessary damage to the bone or the nail.
There are several methods currently being used by orthopedic surgeons when drilling through a bone to anchor an intramedullary nail. The methods have been called the "free-hand" method and the distal aiming device method.
In the free-hand method, the surgeon uses a sharp awl, or drill bit, to locate the starting point under X-ray imaging. The surgeon then rotates the drill point parallel to the line of X-ray and forces the sharp pointed instrument through the bone and through the intramedullary nail. This method, although quick and relatively accurate for surgeons who frequently use it, can increase the amount of radiation the surgeon receives because his or her hand must remain in the path of the X-rays for a period of time.
In the distal aiming device method, a distal aiming device, such as an X-ray transparent target, is used to assist in locating the correct path of transfixion screws for anchoring the intramedullary nail so that the drill bit goes through the hole in the nail and opens a path in the bone for the locking screw. There are distal aiming devices in which a drill template is adjusted and ultimately fixed in the desired position by means of an X-ray image amplifier. For example, Swiss Pat. No. CH-A5 635 998 discloses an aiming device which has an aiming head with a hole for the insertion of a directional socket. The aiming head mounting is positioned in a holder that is connected to the X-ray machine and is suspended from the X-ray machine. This arrangement makes it difficult to position the apparatus and to fix it in position, with resulting unsatisfactory target precision. In addition, the stationary arrangement limits operation.
There is an aiming device that can be used independently of an X-ray machine, described in German industrial design patent U1 84 17 428. A device with a receiving head rests in a holder and is permeable to X-rays, and which accepts a drill bit or a drill wire. Even this improved device, however, has major disadvantages. In particular, the aiming process takes place during the drilling of the bone, which causes considerable darkening of the working field and low image resolution.
U.S. Pat. No. 4,803,976 describes another aiming device which may be held between a radiation source and a radiation receiver, the position of which can be represented visibly by means of an image converter, allowing continuous adjustment of its orientation. The device has a socket for the drill bit and a direction finder which must be maintained in a defined position relative to one another during the drilling process. This device still has the disadvantage that it does not permit direct observation of the drill bit as it drills through the bone and nail because of the obstruction in the radiation field resulting from the power drill which is in the same line of sight as the drill bit.